Effects of coffee on insulin receptor substance and its tyrosine/serine phosphorylation in rats with insulin resistance

CHEN Lin; YU Ming; XIA Juan; GAO Yue-jin

doi:10.3969/j.issn.1002-266X.2014.20.006

Abstract：Objective To observe the effect of coffee on the expression of insulin receptor substance ( IRS)-1 and IRS-2 and their tyrosine/serine phosphorylation in rats with insulin resistance ( IR) and to evaluate its effect on the post-re-ceptor signal transduction in adipose tissues .Methods Totally 40 Wistar rats were randomly divided into the normal con-trol ( NC) group, caffeinated coffee lavage ( CC) group, decaffeinated coffee lavage ( DC) group, and IR ( IR) group, with 10 rats in each group .Except for NC group , the other three groups were given high fat diet .Meanwhile , CC and DC groups, respectively, were treated with caffeinated coffee and decaffeinated coffee daily lavage for 12 weeks.Then the oral glucose tolerance test (OGTT) was given and homeostasis model assessment of insulin resistance (HOMA-IR) was em-ployed to assess the degree of insulin resistance .The levels of IRS-1 and IRS-2 and their mRNA in adipose tissues were de-tected by RT-PCR.And the tyrosine/serine phosphorylation was measured by Western blotting .Results IR group had higher blood glucose levels at the time of 60 and 120 min as compared with NC group (P<0.05, P<0.01, respectively). CC, DC, and IR groups displayed higher fasting insulin levels than NC group (all P<0.05).However, HOMA-IRs of CC, DC, and NC groups were all significantly lower than that of IR group (all P<0.05).Although no significant differ-ences were found in the levels of IRS-1 and IRS-2 as well as IRS-2 mRNA among the four groups (P>0.05), IRS-1 mR-NA of the NC and CC groups was higher than that of the IR group (all P<0.01).Higher tyrosine phosphorylation and low-er serine phosphorylation were exhibited in NC , CC, and DC groups as compared with the IR group (all P<0.05).Con-clusions Insulin resistance induced by high fat diet could be alleviated by coffee , whose mechanism may be explained by its effect on post-receptor signal transduction in adipose tissues by the alteration of IRS-1 mRNA as well as its tyrosine/ser-ine phosphorylation .